The national standard GB7665-87 defines a sensor as: "a device or device that can sense the specified measured object and convert it into a usable signal according to certain rules. It is usually composed of a sensitive element and a conversion element." .
A sensor is a detection device that can sense the measured information and convert the detected information into electrical signals or other required forms of information output according to certain rules to meet the information requirements. Requirements for transmission, processing, storage, display, recording and control.
It is the primary link to realize automatic detection and automatic control.
"Sensor" is defined in the New Webster Dictionary as:
"A device that receives power from one system and usually delivers it in another form to a second system device".
According to this definition, the function of the sensor is to convert one type of energy into another form of energy, so many scholars also use "Transducer" to refer to "Transducer". Sensor - Sensor".
Edit this paragraph
Function
The function of the sensor is often compared to the five major human sensory organs:
Photosensitive sensor—— Visual and sound sensors - hearing
Gas sensors - smell chemical sensors - taste
Pressure-sensitive, temperature-sensitive, fluid sensors - touch
Classification of sensitive components:
①Physical type, based on physical effects such as force, heat, light, electricity, magnetism and sound.
②Chemistry, based on the principles of chemical reactions.
③ Biological type, based on molecular recognition functions such as enzymes, antibodies, and hormones.
Usually according to their basic sensing functions, they can be divided into heat-sensitive elements, light-sensitive elements, gas-sensitive elements, force-sensitive elements, magnetic-sensitive elements, moisture-sensitive elements, sound-sensitive elements, radiation-sensitive elements, and color-sensitive elements. and taste sensitive components (someone once classified sensitive components into 46 categories).
Edit this paragraph
Classification
Sensors can be classified from different perspectives: their conversion principles (the basic physical or chemical effects of sensor operation); Their uses; their output signal types and the materials and processes used to make them, etc.
According to the working principle of the sensor, it can be divided into two categories: physical sensors and chemical sensors:
Classification of sensor working principles Physical sensors apply physical effects, such as piezoelectric effect, magnetic Telestriction phenomenon, ionization, polarization, thermoelectric, photoelectric, magnetoelectric and other effects.
Small changes in the measured signal quantity will be converted into electrical signals.
Chemical sensors include those that are causally related to phenomena such as chemical adsorption and electrochemical reactions. Small changes in the measured signal quantity will also be converted into electrical signals.
Some sensors cannot be classified into either physical or chemical categories.
Most sensors operate on physical principles.
There are many technical problems with chemical sensors, such as reliability issues, the possibility of large-scale production, price issues, etc. If such problems are solved, the application of chemical sensors will grow tremendously.
The application fields and working principles of common sensors are listed in the table below.
1. Sensors are classified according to their uses
Pressure-sensitive and force-sensitive sensors Position sensors
Liquid level sensors Energy consumption sensors
Speed ??sensors Acceleration sensor
Radiation sensor Thermal sensor
24GHz radar sensor
2. Sensors are classified according to their principles
Vibration sensor Humidity sensor Sensors
Magnetic sensors, gas sensors
Vacuum sensors, biosensors, etc.
3. Sensors are classified according to their output signals
Analog sensors - convert measured non-electrical quantities into analog electrical signals.
Digital sensor - converts the measured non-electrical quantity into a digital output signal (including direct and indirect conversion).
Digital sensor - converts the measured signal into a frequency signal or short-period signal output (including direct or indirect conversion).
Switch sensor - When a measured signal reaches a certain threshold, the sensor outputs a set low-level or high-level signal accordingly.
4. Sensors are classified according to their materials.
Under the influence of external factors, all materials will make corresponding and characteristic responses.
Among them, those materials that are most sensitive to external effects, that is, those materials with functional properties, are used to make sensitive components of sensors.
From the perspective of the materials used, sensors can be divided into the following categories:
(1) According to the type of materials used
Metal polymer ceramics Mixture
(2) According to the physical properties of the material: Conductor, Insulator, Semiconductor Magnetic Material
(3) According to the crystal structure of the material:
Single crystal and multiple Crystalline amorphous materials
Sensor development work closely related to the use of new materials can be summarized into the following three directions:
(1) Exploring new materials among known materials phenomena, effects and reactions and then enable their practical use in sensor technology.
(2) Explore new materials and apply known phenomena, effects and reactions to improve sensor technology.
(3) Explore new phenomena, new effects and reactions on the basis of research on new materials, and implement them in sensor technology.
The progress of modern sensor manufacturing depends on the intensity of development of new materials and sensitive components for sensor technology.
The basic trend in sensor development is closely related to the application of semiconductors and dielectric materials.
Table 1.2 gives some materials that can be used in sensor technology and can convert energy forms.
5. Sensors are classified according to their manufacturing process
Integrated sensors Thin film sensors Thick film sensors Ceramic sensors
Integrated sensors are produced using standard silicon-based semiconductor integrated circuits Made with advanced process technology.
Usually some circuits used for preliminary processing of the signal under test are also integrated on the same chip.
Thin film sensors are formed by depositing thin films of corresponding sensitive materials on a dielectric substrate (substrate).
When using a hybrid process, part of the circuit can also be fabricated on this substrate.
Thick film sensors are made by coating the slurry of corresponding materials on a ceramic substrate. The substrate is usually made of Al2O3, and then heat treated to form a thick film.
Ceramic sensors are produced using standard ceramic processes or some variant thereof (sol-gel, etc.).
After appropriate preparatory operations, the formed components are sintered at high temperatures.
There are many different characteristics between the two processes of thick film and ceramic sensors. In some respects, the thick film process can be considered a variant of the ceramic process.
Each process technology has its own advantages and disadvantages.
Due to the low capital investment required for research, development and production, as well as the high stability of sensor parameters, the use of ceramic and thick film sensors is more reasonable.
(Provided by HVAC experts at Konglu.com)
6. Sensors are classified according to different measurement purposes
Physical sensors use certain physical properties of the substance being measured. Characteristics with significant changes in properties.
Chemical sensors are made of sensitive elements that can convert chemical quantities such as the composition and concentration of chemical substances into electrical quantities.
Biosensors are sensors made by utilizing the characteristics of various organisms or biological substances to detect and identify chemical components in organisms.
Edit this paragraph
Characteristics
Static characteristics of the sensor
The static characteristics of the sensor refer to the static input signal and the output of the sensor. The relationship between the quantity and the input quantity.
Since the input and output quantities are independent of time at this time, the relationship between them, that is, the static characteristics of the sensor, can be determined by an algebraic equation that does not contain time variables, or by using the input quantity as the abscissa, Describe the characteristic curve drawn by taking the corresponding output quantity as the ordinate.
The main parameters characterizing the static characteristics of the sensor are: linearity, sensitivity, hysteresis, repeatability, drift, etc.
(1) Linearity: refers to the degree to which the actual relationship curve between sensor output and input deviates from the fitted straight line.
It is defined as the ratio of the maximum deviation value between the actual characteristic curve and the fitted straight line within the full-scale range and the full-scale output value.
(2) Sensitivity: Sensitivity is an important indicator of the static characteristics of the sensor.
It is defined as the ratio of the increment of the output quantity to the corresponding increment of the input quantity that caused the increment.
Use S to represent sensitivity.
(3) Hysteresis: The phenomenon that the input and output characteristic curves of the sensor do not overlap when the input quantity changes from small to large (forward stroke) and from large to small (reverse stroke) is called hysteresis.
For input signals of the same size, the forward and reverse stroke output signals of the sensor are not equal in size. This difference is called the hysteresis difference.
(4) Repeatability: Repeatability refers to the degree to which the characteristic curve obtained by the sensor is inconsistent when the input value changes continuously multiple times across the full range in the same direction.
(5) Drift: The drift of the sensor means that the sensor output changes with time when the input quantity remains unchanged. This phenomenon is called drift.
There are two reasons for drift: one is the structural parameters of the sensor itself; the other is the surrounding environment (such as temperature, humidity, etc.).
Sensor dynamic characteristics
The so-called dynamic characteristics refer to the characteristics of the output of the sensor when the input changes.
In actual work, the dynamic characteristics of a sensor are often expressed by its response to certain standard input signals.
This is because the sensor's response to the standard input signal is easy to obtain experimentally, and there is a certain relationship between its response to the standard input signal and its response to any input signal, which is often known. The former can infer the latter.
The most commonly used standard input signals are step signal and sinusoidal signal, so the dynamic characteristics of the sensor are also commonly expressed by step response and frequency response.
Sensor linearity
Typically, the actual static characteristic output of a sensor is a curve rather than a straight line.
In actual work, in order to make the instrument have a uniform scale reading, a fitting straight line is often used to approximately represent the actual characteristic curve. Linearity (nonlinear error) is a performance index of this approximation degree.
There are many ways to select the fitting straight line.
For example, the theoretical straight line connecting the zero input and full-scale output points is used as the fitting straight line; or the theoretical straight line with the smallest sum of square deviations from each point on the characteristic curve is used as the fitting straight line. The straight line is called the least squares fitted straight line.
The following are schematic diagrams of several fitting methods.
Theoretical fitting, zero-crossing rotation fitting, endpoint connection fitting
Sensitivity of the sensor
Sensitivity refers to the change in output of the sensor under steady-state working conditions The ratio of △y to the change in input quantity △x.
It is the slope of the output-input characteristic curve.
If there is a linear relationship between the sensor's output and input, the sensitivity S is a constant.
Otherwise, it will change with the input amount.
The dimension of sensitivity is the ratio of the dimensions of the output and input quantities.
For example, for a displacement sensor, when the displacement changes by 1mm, the output voltage changes by 200mV, then its sensitivity should be expressed as 200mV/mm.
When the dimensions of the sensor's output and input are the same, the sensitivity can be understood as the amplification factor.
Improve the sensitivity and get higher measurement accuracy.
However, the higher the sensitivity, the narrower the measurement range and the worse the stability.
Sensor resolution
Resolution refers to the ability of a sensor to detect the smallest change in a measured value.
That is, if the input quantity changes slowly from some non-zero value.
When the input change value does not exceed a certain value, the output of the sensor will not change, that is, the sensor cannot distinguish the change in the input quantity.
Only when the input changes exceed the resolution, its output will change.
Usually the resolution of the sensor at each point within the full-scale range is not the same. Therefore, the maximum change value in the input quantity that can cause a step change in the output quantity in the full-scale range is often used as an indicator to measure the resolution. .
If the above indicators are expressed as a percentage of full scale, it is called resolution.
Resolution has a negative correlation with sensor stability.
Edit this paragraph
24GHz radar sensor
The 24GHz radar sensor senses objects by emitting and receiving microwaves with a frequency of about 24.125GHz
< p> 24GHZ radar sensorexists, measuring the moving speed of an object, stationary distance, angle of the object, etc. It uses planar microstrip technology and is small in size.
It has the characteristics of high degree of integration, sensitive sensing and no need for contact.
The 24GHz radar sensor is a replacement device that can convert microwave echo signals into an electrical signal. It is used in radar speedometers, water level gauges, car ACC assisted cruise systems, automatic door sensors, etc. core chip.
Edit this paragraph
Resistive sensor
Resistive sensors are physical quantities that will be measured, such as displacement, deformation, force, acceleration, humidity, temperature, etc. A device that converts a formula into a resistance value.
Mainly include resistance strain gauge, piezoresistive, thermal resistance, heat sensitive, gas sensitive, humidity sensitive and other resistive sensing devices.
Load cell
The load cell is a force-to-electric conversion device that can convert gravity into an electrical signal. It is a key component of electronic weighing instruments.
There are many kinds of sensors that can realize force-to-electricity conversion. Common ones include resistance strain type, electromagnetic force type and capacitive type.
The electromagnetic force type is mainly used in electronic balances, the capacitive type is used in some electronic crane scales, and the vast majority of weighing instrument products use resistance strain type load cells.
Resistance strain gauge load cells have a simple structure, high accuracy, wide application, and can be used in relatively poor environments.
Therefore, resistance strain gauge load cells have been widely used in weighing instruments.
Edit this paragraph
Resistance strain gauge sensor
The resistance strain gauge in the sensor has a metal strain effect, that is, it produces mechanical deformation under the action of external force, thus The resistance value changes accordingly.
Resistance strain gauges are mainly divided into two types: metal and semiconductor. Metal strain gauges are divided into wire type, foil type and film type.
Semiconductor strain gauges have the advantages of high sensitivity (usually dozens of times that of wire and foil types) and small lateral effects.
Edit this paragraph
Piezoresistive sensor
Piezoresistive sensor is based on the piezoresistive effect of semiconductor material through diffusion of resistance on the substrate of semiconductor material. manufactured devices.
The substrate can be directly used as a measurement sensing element, and the diffusion resistor is connected in the form of a bridge within the substrate.
When the substrate is deformed by external force, each resistance value will change, and the bridge will produce a corresponding unbalanced output.
The substrate (or diaphragm) materials used as piezoresistive sensors are mainly silicon wafers and germanium wafers. Silicon piezoresistive sensors made of silicon wafers as sensitive materials are becoming more and more popular. Attention, especially the most common application of solid-state piezoresistive sensors for measuring pressure and speed.
Edit this paragraph
Thermal resistance sensor
Thermal resistance temperature measurement is based on the characteristic that the resistance value of the metal conductor increases with the increase of temperature. measured.
Most thermal resistors are made of pure metal materials. The most commonly used ones are platinum and copper. In addition, thermal resistors have now begun to be made of materials such as nickel, manganese and rhodium.
Thermal resistance sensors mainly use the characteristic that resistance value changes with temperature to measure temperature and temperature-related parameters.
This kind of sensor is more suitable for occasions where the temperature detection accuracy is relatively high.
Currently, the most widely used thermal resistance materials are platinum, copper, nickel, etc. They have the characteristics of large temperature coefficient of resistance, good linearity, stable performance, wide operating temperature range, and easy processing.
Used to measure the temperature in the range of -200℃～+500℃.
Classification of thermal resistance sensors:
1. NTC thermal resistance sensor:
This type of sensor is a negative temperature coefficient sensor, that is, the sensor resistance decreases as the temperature increases.
2. PTC thermal resistance sensor:
This type of sensor is a positive temperature coefficient sensor, that is, the sensor resistance increases as the temperature increases.
Edit this paragraph
Laser sensor
A sensor that uses laser technology for measurement.
It consists of laser, laser detector and measurement circuit.
Laser sensor is a new type of measuring instrument. Its advantages are that it can achieve non-contact long-distance measurement, fast speed, high precision, large measuring range, strong resistance to light and electrical interference, etc.
When the laser sensor works, the laser emitting diode first emits laser pulses at the target.
After being reflected by the target, the laser light scatters in all directions.
Part of the scattered light returns to the sensor receiver, is received by the optical system, and is imaged onto the avalanche photodiode.
The avalanche photodiode is an optical sensor with an internal amplification function, so it can detect extremely weak light signals and convert them into corresponding electrical signals.
Non-contact long-distance measurement can be achieved by utilizing the characteristics of laser such as high directivity, high monochromaticity and high brightness.
Laser sensors are commonly used to measure physical quantities such as length (ZLS-Px), distance (LDM4x), vibration (ZLDS10X), speed (LDM30x), orientation, etc. They can also be used for flaw detection and monitoring of air pollutants. .
Edit this paragraph
Temperature sensor
1. Room temperature tube temperature sensor:
The room temperature sensor is used to measure the indoor and outdoor ambient temperatures, and the tube temperature sensor is used to measure the tube wall temperature of the evaporator and condenser.
The shapes of the room temperature sensor and the tube temperature sensor are different, but the temperature characteristics are basically the same.
According to the temperature characteristics, there are two types of room temperature tube temperature sensors currently used by Midea: 1. The constant B value is 4100K±3%, and the reference resistance is 25°C and the corresponding resistance is 10KΩ±3%.
The higher the temperature, the smaller the resistance; the lower the temperature, the greater the resistance.
The farther away from 25℃, the larger the corresponding resistance tolerance range; at 0℃ and 55℃, the corresponding resistance tolerance is about ±7%; while below 0℃ and above 55℃, for different suppliers, Resistor tolerances will vary.
The higher the temperature, the smaller the resistance; the lower the temperature, the greater the resistance.
The farther away from 25℃, the larger the corresponding resistance tolerance range.
2. Exhaust temperature sensor:
The exhaust temperature sensor is used to measure the exhaust temperature at the top of the compressor. The constant B value is 3950K±3%, and the reference resistance is 90°C and the corresponding resistance is 5KΩ±3%.
3. . Module temperature sensor: The module temperature sensor is used to measure the temperature of the frequency conversion module (IGBT or IPM). The model of the temperature sensing head currently used is 602F-3500F. The reference resistance is 25°C and the corresponding resistance is 6KΩ±1%.
The corresponding resistance values ??of several typical temperatures are: -10℃ → (25.897─28.623) KΩ; 0℃ → (16.3248─17.7164) KΩ; 50℃ → (2.3262─2.5153) KΩ; 90 ℃ → (0.6671─0.7565) KΩ.
There are many types of temperature sensors. The most commonly used ones are thermal resistors: PT100, PT1000, Cu50, Cu100; thermocouples: B, E, J, K, S, etc.
There are not only many types of temperature sensors, but also various combinations. Appropriate products should be selected according to different places.
Temperature measurement principle: According to the principle that the resistance value of the resistor and the potential of the thermocouple change regularly with different temperatures, we can get the temperature value that needs to be measured.
(Provided by HVAC experts at Konglu.com)
Edit this paragraph
Photosensitive sensor
Photosensitive sensor is one of the most common sensors First, it has many types, mainly including: photoelectric tube, photomultiplier tube, photoresistor, phototransistor, solar cell, infrared sensor, ultraviolet sensor, optical fiber photoelectric sensor, color sensor, CCD and CMOS image sensor, etc.
Its sensitive wavelength is near the wavelength of visible light, including infrared wavelengths and ultraviolet wavelengths.
The light sensor is not only limited to the detection of light, it can also be used as a detection element to form other sensors to detect many non-electric quantities, as long as these non-electric quantities are converted into changes in optical signals.
Light sensors are currently one of the most produced and widely used sensors. They play a very important role in automatic control and non-electrical measurement technology.
The simplest light sensor is a photoresistor, which generates an electric current when photons strike the joint.
Edit this paragraph
Humidity sensor information
Polymer capacitive humidity sensors are usually on insulating substrates such as glass, ceramics, silicon and other materials , use screen printing or vacuum coating process to make electrodes, and then use dipping or other methods to coat the moisture-sensitive glue on the electrodes to make capacitive elements.
In atmospheric environments with different relative humidity, the capacitance value of the humidity sensor changes regularly due to the adsorption of water molecules by the moisture-sensitive film. This is the basic mechanism of the humidity sensor.
The temperature characteristics of polymer capacitive components are affected by changes in the dielectric constant ε of the polymer as the medium and the dielectric constant ε of the adsorbed water molecules that are affected by temperature, as well as the temperature characteristics of the component. The geometric dimensions are affected by factors such as thermal expansion coefficient changes.
According to the Debye theory, the dielectric constant ε of a liquid is a dimensionless constant related to temperature and frequency.
The ε of water molecules is 78.36 at T=5℃ and 79.63 at T=20℃.
The relationship between organic matter ε and temperature varies from material to material and does not follow a completely proportional relationship.
In some temperature areas, ε shows an upward trend with T, and in some temperature areas, ε decreases with the increase of T.
In the analysis of the moisture-sensing mechanism of polymer humidity-sensitive capacitive elements, most literature believes that polymers have a small dielectric constant. For example, polyimide has a dielectric constant of 3.0 at low humidity. 1.3.8.
The dielectric constant of water molecules is dozens of times that of polymer ε.
Therefore, after the polymer medium absorbs moisture, due to the existence of the dipole moment of water molecules, the dielectric constant of the water-absorbing heterogeneous layer is greatly increased. This is the additive nature of the composite dielectric constant of the multi-phase medium. decided.
Due to the change of ε, the capacitance C of the humidity-sensitive capacitive element is proportional to the relative humidity.
In the design and production process, it is difficult to achieve linearity in the entire humidity range of the moisture sensing characteristics.
As a capacitor, the thickness d of the polymer dielectric film and the effective area S of the plate capacitor are also related to temperature.
Changes in the geometric dimensions of the medium caused by temperature changes will affect the C value.
The average thermal expansion coefficient of polymers can reach a level of magnitude.
For example, the average thermal expansion coefficient of nitrocellulose is 108x10-5/℃.
As the temperature rises, the medium film thickness d increases, making a negative contribution to C; however, the expansion of the moisture-sensitive film increases the amount of water adsorbed by the medium, which makes a positive contribution to C.
It can be seen that the temperature characteristics of humidity-sensitive capacitors are dominated by a variety of factors, with different temperature drifts in different humidity ranges; different temperature coefficients in different temperature zones; and different temperature characteristics of different humidity-sensitive materials.
In short, the temperature coefficient of the polymer humidity sensor is not a constant, but a variable.
Therefore, usually sensor manufacturers can linearize the sensor in the range of -10-60 degrees Celsius to reduce the impact of temperature on the humidity sensor.
The relatively high-quality products mainly use polyamide resin. The product structure is as follows: gold electrodes are made by vacuum evaporation on a borosilicate glass or sapphire substrate, and then the moisture-sensitive dielectric material is sprayed (as mentioned above) A flat moisture-sensitive film is then evaporated onto the film with gold electrodes.
The capacitance value of the humidity sensor is proportional to the relative humidity, and the linearity is about ±2%.
Although the humidity measurement performance is acceptable, its temperature resistance and corrosion resistance are not ideal. For use in the industrial field, its lifespan, temperature resistance, stability, and corrosion resistance need to be further improved. improve.
Ceramic humidity sensor is a new type of sensor that has been vigorously developed in recent years.
The advantages are high temperature resistance, humidity lag, fast response speed, small size, and easy for mass production. However, due to the porous material, it has a great impact on dust, and daily maintenance is frequent. It often requires electric heating and cleaning. Product quality, easily affected by humidity, poor linearity in low-humidity and high-temperature environments, especially short service life, and poor long-term reliability are issues that this type of humidity-sensitive sensor needs to urgently solve.
In the current development and research of humidity sensors, resistive humidity sensors should be most suitable for the field of humidity control. Its representative product, lithium chloride humidity sensor, has stability, temperature resistance and long service life. This is an important advantage. Lithium chloride humidity sensors have a history of production and research for more than fifty years. They have a variety of product types and production methods, all of which apply the various advantages of lithium chloride humidity sensors. Especially the most stable.
Lithium chloride humidity-sensing devices are electrolytic moisture-sensing materials. Among many moisture-sensing materials, they were first noticed and used in the manufacture of moisture-sensing devices. Lithium chloride electrolyte moisture-sensing liquids are based on the equivalent Conductance decreases as solution concentration increases.
The principle of electrolyte dissolving in water reduces the vapor pressure on the water surface to achieve moisture sensing.
The substrate structure of the lithium chloride humidity sensor is divided into columnar and combed shapes. The moisture-sensitive liquid coated with lithium chloride polyvinyl alcohol as the main component and the gold electrode are made of lithium chloride humidity sensor. of three components.
Over the years, product manufacturing has been continuously improved and product performance has been continuously improved. The unique long-term stability of the lithium chloride humidity sensor is irreplaceable by other humidity-sensing materials and is also the most important performance of the humidity sensor.
In the product production process, the preparation of the moisture-sensitive mixture and strict control of the process are the key to maintaining and exerting this characteristic.
Edit this paragraph
Hysteresis characteristics
The hysteresis characteristics characterize the sensor between the forward (input volume increases) and reverse (input volume decreases) stroke. The degree of inconsistency between the output-input characteristic curves is usually expressed as the percentage of the maximum difference ΔMAX between the two curves and the full-scale output F·S.
Hysteresis can be caused by the absorption of energy by components within the sensor.
Interface sensor
Weidmüller sensor/actuator interface products can be directly connected to the fieldbus by installing the corresponding bus protocol adapter.
Can support Profibus-DP, CANopen, DeviceNet, Interbus and ASi fieldbus protocols.
Passive sensor/actuator interface products (SAI)
The protection level reaches IP68 and can be installed directly without protection.
Save installation materials, time and space.
Provides 4.6.8-channel splitter, each channel has 3-pin, 4-pin and 5-pin structures (providing one and two-channel signals).
There are types with wiring covers (standard type) and prefabricated types with cables.
Products with metal shells are also available, suitable for the food industry.
With indication of signal and power.
Active Sensor/Actuator Interface Products (SAI)
By installing the corresponding bus protocol adapter, SAI products can be directly connected to the fieldbus.
Can support Profibus-DP, CANopen, DeviceNet, Interbus and ASi fieldbus protocols.
Products with two protection levels are provided: IP67 (the bus connection method is circular connector connection), IP68 (the bus connection method is self-assembly type).
Provides five input and output products: 8DI, 8DO, 8DI/4DO, 16DI, and 8DI/8DO.
Development trends of sensors
Adopt new principles and develop new sensors
Vigorously develop physical sensors (because some structural types cannot meet the requirements)
Integration of sensors
Multifunctionalization of sensors
Intelligence of sensors (Smart Sensor)
Research biological senses and develop bionic sensors.
Edit this paragraph
Working process example
Provide ±15V power to the sensor, the crystal oscillator in the excitation circuit generates a 400Hz square wave, and the TDA2030 power The amplifier generates AC excitation power, which is transmitted from the stationary primary coil to the rotating secondary coil through the energy toroidal transformer T1. The resulting AC power is passed through the rectifier and filter circuit on the shaft to obtain a ±5V DC power supply. This power supply is used as the operational amplifier AD822 The working power supply; the high-precision regulated power supply composed of the reference power supply AD589 and the dual operational amplifier AD822 produces a ±4.5V precision DC power supply. This power supply serves as both a bridge power supply and a working power supply for the amplifier and V/F converter.
When the elastic shaft is torsion, the mV-level strain signal detected by the strain bridge is amplified into a strong signal of 1.5v±1v by the instrument amplifier AD620, and then converted into a frequency signal through the V/F converter LM131 , transmitted from the rotating primary coil to the stationary secondary coil through the signal toroidal transformer T2, and then filtered and shaped by the signal processing circuit on the housing to obtain a frequency signal proportional to the torque on the elastic bearing, which is a TTL level , which can be provided to a special secondary instrument or frequency meter for display or directly sent to a computer for processing.
Since there is only a few tenths of a millimeter gap between the dynamic and static rings of the resolver, and the upper part of the sensor shaft is sealed in a metal shell, forming an effective shield, it has strong anti-interference. ability.